There can be error in obits, even if the deceased was the author, or they type setter was in a rush. This one (this reprint dated 1928 from the original in 1891) is rich in specific detail, it's a genealogists dream.
In regard to his military service. The loose dates in the obit of his service indicate he might have served in 1st of the Florida (Seminole) Wars. Start with googling First Seminole War, then start reading. Volunteers and militias were from the parts of the south your ancestor was from, it's absolutely makes sense.
In regard to finding documentation for the events in his life, in particular his marriages, and a possible bap record for him, etc.
First, try and match some of the location data found in the obit to census data. The 1840 census and prior only list the head of household, but they should be investigated. Finding a match of location on a census to the data in the obit encourages that the data in the obit has veracity.
Once you've established a location and time-period, search the Library Catalog on the familysearch.org website, and see what films of records are available for the area and time-period, ie Church records, land records, wills, probate, etc. You can order the film online and view them at a local Family History Center. The "how to, where to" info is on the familysearch.org website.
Investigate the holdings of the local Historical Society, google the area and historical society, genealogical society. Most US counties have their own genweb site page that list the resources available. Google the county name and state, and "genealogy".
I suspect the chance of finding detailed evidence on the internet is remote, but the internet is very effective to help find the resources.